Technical Field
The disclosure relates to a nickel hydrogen battery.
Description of Related Art
A nickel hydrogen battery is widely used in the fields of cellular phones, personal computers, electric tools, hybrid vehicles, electric vehicles, etc. Such a nickel hydrogen battery is used as a primary battery that can be discharged only once, and it is also used as a secondary battery (nickel hydrogen storage battery) that can be charged and discharged repeatedly.
In the field of nickel hydrogen batteries, there has been an attempt to suppress a decrease in the capacity of nickel hydrogen batteries, focusing on electrolytes and electrode active materials. For example, in Patent Literature 1, it is disclosed to suppress a decrease in the capacity of a cylindrical nickel hydrogen storage, by defining the amount of zinc (Zn) added to a nickel (Ni) cathode and the alkali concentration of an alkaline electrolyte.    Patent Literature 1: Japanese Patent Application Laid-Open No. 2012-069510    Non-Patent Literature 1: Tao Yang, et al., “Inorganic Chemistry”, 2007, 46, p. 2342-2344    Non-Patent Literature 2: V. Pralong, et al., “Inorganic Chemistry”, 2009, 48, p. 6835-6844    Non-Patent Literature 3: Yuichi Sato, “SCIENCE REPORTS OF RESEARCH INSTITUTE FOR ENGINEERING, KANAGAWA UNIVERSITY, NO. 32”, Research Institute for Engineering, Kanagawa University, issued on Nov. 30, 2009, No. 32, p. 109-113
However, a conventional nickel hydrogen battery that uses, as a cathode active material, a β-type nickel hydroxide (β-Ni(OH)2) having a layered structure as disclosed in Patent Literature 1, is problematic in that it cannot sufficiently suppress a decrease in battery voltage after charge.